The process of making bread or other leavened food products includes several stages including mixing, leavening and baking. During mixing, the baker mixes and blends flour with a leavening agent, such as yeast or a chemical leavening agent, sugar, salt, water, and/or other ingredients in accordance with a particular recipe to form a bread dough. An exemplary chemical leavening agent is baking powder, but most bread doughs use a yeast. Mixing generally is controlled by weight, volume, and time measurements.
After the mixing stage, the dough is allowed to rise during the leavening stage. Upon mixing, the leavening agent interacts with other ingredients to produce ethanol (C2H5OH) and carbon dioxide (CO2). The ethanol provides a distinct flavor and odor while the carbon dioxide creates gas pockets inside the dough that allow the dough to rise and influence the finished texture of the bread. The leavening stage generally is controlled using a time and temperature (and possibly humidity) profile.
The leavening stage may include a fermentation phase and a proofing phase. Depending on the recipe, the fermentation phase may be repeated after a punching phase during which the dough is physically compressed before shaping the dough and allowing the dough to rise again in a second fermentation phase.
When the baker is satisfied with the amount the dough has risen, the baker bakes the bread, or other food product, at a higher temperature. As the dough begins baking, some of the yeast continues to generate additional gas and results in an additional stage of rising called ovenspring. Eventually the temperature of the dough reaches a point where yeast activity stops and no additional carbon dioxide is generated. The baking stage is controlled primarily by a time and temperature profile in an oven.
The amount or rate of production of carbon dioxide produced by various leavening agents generally changes over time. Differences in the amount or rate of carbon dioxide produced by various leavening agents has been used to select the optimum leavening agents for particular recipes. Chemical leavening agents generally produce carbon dioxide at a substantially constant rate, the amount and duration of the production generally being dependant on the amount of chemical leavening agent and reactants in the recipe.
The fermentation action of the yeast that results in carbon dioxide production varies with the yeast variety, recipe, temperature, and other factors. Thus, when yeast is used as the leavening agent, carbon dioxide production is more variable than when the baker uses a chemical leavening agent.
Common yeast fermentation times are on the order of several hours, and common proofing times are on the order of about one hour. Dough that spends too much or too little time in the fermentation or proofing phases may have undesirable characteristics. For example, over-fermentation can lead to the production of ascorbic acid from oxidation, which may change the flavor of a finished loaf of bread. Under-proofing results in tight grains, ripped-out break and shred and low loaf volume, while over-proofing leads to open grains, caps, and asymmetrical loaves of bread. Commercial baking systems process large numbers of baked goods, such as bread loaves, in large capacity ovens. Any reduction in the production time can lead to substantial savings either through increased throughput or reduced capital investment.